This section provides background information related to the present disclosure which is not necessarily prior art.
Passive inflatable restraint systems are used in a variety of applications, such as motor vehicles. Certain types of passive inflatable restraint systems minimize occupant injuries by using a pyrotechnic gas generant to inflate an airbag cushion (e.g., gas initiators and/or inflators) or to actuate a seatbelt tensioner (e.g., micro gas generators), for example. Automotive airbag inflator performance and safety requirements are continually increasing to enhance passenger safety, while concurrently striving to reduce manufacturing costs.
Many conventional gas generant grains are pressed or extruded for use in airbag inflators. Grains with large or complicated geometry are often pressed to achieve the desired designs. Such pressed grains typically are relatively large and considered to be monolithic bodies, as they are a single unitary monolithic grain structure. Monolithic gas generant grain designs have many advantages, such as repeatable and well controlled combustion, by way of non-limiting example. However, they have several potential disadvantages. Large pressed grains require large press equipment (typically a hydraulic press) that is very expensive and often requires a slower cycle time, which in turn increases processing costs. These pressed grains also tend to be somewhat fragile. Broken grains can occur during processing, shipping, or during the life of the product after they are loaded into an airbag inflator. Broken grains during processing results in increased cost due to product scrap, while broken grains during life cycle can be more serious in that they have the potential to result in performance variation within the inflatable restraint device. Thus, it would be desirable to have robust pressed gas generant grains that have reduced breakage and reduced manufacturing costs, while exhibiting many of the performance advantages associated with conventional pressed monolithic grains.